How do receptor tyrosine kinases (RTKs) activate downstream signaling?

How do receptor tyrosine kinases (RTKs) activate downstream signaling?

• A. RTKs dimerize and autophosphorylate upon ligand binding.
• B. RTKs become inactive and stop transmitting signals.
• C. RTKs are exclusively activated by G-proteins.
• D. RTKs only function in the presence of calcium ions.

Answer: (A)

Receptor tyrosine kinases (RTKs) play a pivotal role in cell signaling, particularly in the response to growth factors and hormones. When a ligand binds to the extracellular domain of RTKs, it induces the dimerization of two RTK molecules. This dimerization leads to autophosphorylation, which is the process where the kinases add phosphate groups to specific tyrosine residues on themselves. This autophosphorylation is crucial because it creates docking sites for downstream signaling proteins that contain specific domains, such as SH2 (Src Homology 2) domains, allowing for the recruitment and activation of various intracellular signaling cascades. The phosphorylation of the tyrosine residues activates a range of signaling pathways, such as the MAPK pathway, which is involved in cell growth, differentiation, and survival. This activation serves as a critical relay mechanism, facilitating communication from the extracellular environment to the inside of the cell, ultimately influencing cellular outcomes such as proliferation and metabolism. The other choices do not align with the established understanding of how RTKs function in signaling. For instance, the notion that RTKs become inactive upon ligand binding contradicts their well-known role in signal transduction, which relies on their activation. Additionally,

Receptor tyrosine kinases (RTKs) play a pivotal role in cell signaling, particularly in the response to growth factors and hormones. When a ligand binds to the extracellular domain of RTKs, it induces the dimerization of two RTK molecules. This dimerization leads to autophosphorylation, which is the process where the kinases add phosphate groups to specific tyrosine residues on themselves. This autophosphorylation is crucial because it creates docking sites for downstream signaling proteins that contain specific domains, such as SH2 (Src Homology 2) domains, allowing for the recruitment and activation of various intracellular signaling cascades.

The phosphorylation of the tyrosine residues activates a range of signaling pathways, such as the MAPK pathway, which is involved in cell growth, differentiation, and survival. This activation serves as a critical relay mechanism, facilitating communication from the extracellular environment to the inside of the cell, ultimately influencing cellular outcomes such as proliferation and metabolism.

The other choices do not align with the established understanding of how RTKs function in signaling. For instance, the notion that RTKs become inactive upon ligand binding contradicts their well-known role in signal transduction, which relies on their activation. Additionally,